Supramolecular Assemblies of Fluorescent Nitric Oxide Photoreleasers with Ultrasmall Cyclodextrin Nanogels

Developing biocompatible nitric oxide (NO) photoreleasing nanoconstucts is of great interest in view of the large variety of biological roles that NO plays and the unique advantage light offers in controlling NO release in space and time. In this contribution, we report the supramolecular assemblies of two NO photodonors (NOPDs), NBF-NO and RHD-NO, as water-dispersible nanogels, ca. 10 nm in diameter, based on γ-cyclodextrins (γ-CDng). These NOPDs, containing amino-nitro-benzofurazan and rhodamine chromophores as light harvesting antennae, can be activated by visible light, are highly hydrophobic and can be effectively entrapped within the γ-CDng. Despite being confined in a very restricted environment, neither NOPD suffer self-aggregation and preserve their photochemical and photophysical properties well. The blue light excitation of the weakly fluorescent γ-CDng/NBF-NO complex results in effective NO release and the concomitant generation of the highly green, fluorescent co-product, which acts as an optical NO reporter. Moreover, the green light excitation of the persistent red fluorescent γ-CDng/RHD-NO triggers NO photorelease without significantly modifying the emission properties. The activatable and persistent fluorescence emissions of the NOPDs are useful for monitoring their interactions with the Gram-positive methicillin-resistant Staphylococcus aureus, whose growth is significantly inhibited by γ-CDng/RHD-NO upon green light irradiation.

Functionalization of Polyhydroxyalkanoates (PHA)-Based Bioplastic with Phloretin for Active Food Packaging: Characterization of Its Mechanical, Antioxidant, and Antimicrobial Activities

The formulation of eco-friendly biodegradable packaging has received great attention during the last decades as an alternative to traditional widespread petroleum-based food packaging. With this aim, we designed and tested the properties of polyhydroxyalkanoates (PHA)-based bioplastics functionalized with phloretin as far as antioxidant, antimicrobial, and morpho-mechanic features are concerned. Mechanical and hydrophilicity features investigations revealed a mild influence of phloretin on the novel materials as a function of the concentration utilized (5, 7.5, 10, and 20 mg) with variation in FTIR e RAMAN spectra as well as in mechanical properties. Functionalization of PHA-based polymers resulted in the acquisition of the antioxidant activity (in a dose-dependent manner) tested by DPPH, TEAC, FRAR, and chelating assays, and in a decrease in the growth of food-borne pathogens (Listeria monocytogenes ATCC 13932). Finally, apple samples were packed in the functionalized PHA films for 24, 48, and 72 h, observing remarkable effects on the stabilization of apple samples. The results open the possibility to utilize phloretin as a functionalizing agent for bioplastic formulation, especially in relation to food packaging.

Evaluation of the In Vitro Antifungal Activity of Novel Arylsulfonamides against Candida spp

The antifungal activity of molecules belonging to the arylsulfonamide chemotype has previously been demonstrated. Here, we screened arylsulfonamide-type compounds against a range of Candida spp. and further established the structure-activity relationship based on a "hit compound". A series of four sulfonamide-based compounds, N-(4-sulfamoylbenzyl) biphenyl-4-carboxamide (3), 2,2-diphenyl-N-(4-sulfamoylbenzyl) acetamide (4), N-(4-sulfamoylphenethyl) biphenyl-4-carboxamide (5) and 2,2-diphenyl-N-(4-sulfamoylphenethyl) acetamide (6), were tested against the American Type Culture Collection (ATCC) and clinical strains of C. albicans, C. parapsilosis and C. glabrata. Based on the fungistatic potential of prototype 3, a further subset of compounds, structurally related to hit compound 3, was synthesized and tested: two benzamides (10-11), the related amine 4-[[(4-4-((biphenyl-4-ylmethylamino)methyl) benzenesulfonamide (13) and the corresponding hydrochloride, 13^.HCl. Both amine 13 and its hydrochloride salt had fungicidal effects against Candida glabrata strain 33 (MFC of 1.000 mg/mL). An indifferent effect was detected in the association of the compounds with amphotericin B and fluconazole. The cytotoxicity of the active compounds was also evaluated. This data could be useful to develop novel therapeutics for topical use against fungal infections.

Harnessing the power of PLA-PEG Nanoparticles for Linezolid delivery against Methicillin-Resistant Staphylococcus aureus

This study deals with the development of novel poly(lactic acid-co-polyethylene glycol) nanoparticles (PLA-PEG NPs) for the efficient and prolonged delivery of Linezolid (LNZ), a synthetic antibacterial agent used against methicillin-resistant Staphylococcus aureus (MRSA). A two-step synthetic strategy based on carbodiimide coupling and copper-catalyzed azide-alkyne cycloaddition was first exploited for the conjugation of PLA with PEG. The encapsulation of LNZ into medium-molecular-weight PLA-PEG NPs was carried out by different methods including nanoprecipitation and dialysis. The optimal PLA-PEG@LNZ nanoformulation resulted in 3.5% LNZ payload (15% encapsulation efficiency, with a 10:3 polymer to drug ratio) and sustained release kinetics with 65% of entrapped antibiotic released within 80 h. Moreover, the zeta potential values (from -31 to -39 mV) indicated a good stability without agglomeration even after freeze-drying and lyophilization. The PLA-PEG@LNZ NPs exerted antimicrobial activity against a panel of Gram-positive bacteria responsible for human infections, such as S. aureus, MRSA, S. epidermidis, S. lugdunensis and vancomycin resistant Enterococcus faecium (VRE). Moreover, PLA-PEG@LNZ NPs showed inhibitory activity on both planktonic growth and preformed biofilm of MRSA. The antibacterial activity of LNZ incorporated in polymeric NPs was well preserved and the nanosystem served as an antibiotic enhancer with a potential role in MRSA-associated infections management.

Composition and Biological Properties of Blanched Skin and Blanch Water Belonging to Three Sicilian Almond Cultivars

The almond industry produces, by bleaching and stripping, two by-products: blanched skin (BS) and blanch water (BW). The aim of this study was to investigate the nutritional and polyphenolic profile, as well as the antioxidant, antimicrobial, antiviral, and potential prebiotic effects of BS and BW from three different Sicilian cultivars. The total phenols and flavonoids contents were ≥1.72 and ≥0.56 g gallic acid equivalents and ≥0.52 and ≥0.18 g rutin equivalents/100 g dry extract (DE) in BS and BW, respectively. The antioxidant activity, evaluated by 2,2-diphenyl-1-picrylhydrazyl scavenging ability, trolox equivalent antioxidant capacity, ferric-reducing antioxidant power, and oxygen radical absorbance capacity, was ≥3.07 and ≥0.83 g trolox equivalent/100 g DE in BS and BW, respectively. Isorhamnetin-3-O-glucoside was the most abundant flavonoid detected in both by-products. No antimicrobial effect was recorded, whereas BS samples exerted antiviral activity against herpes simplex virus 1 (EC₅₀ 160.96 μg/mL). BS also showed high fibre (≥52.67%) and protein (≥10.99) contents and low fat (≤15.35%) and sugars (≤5.55%), making it nutritionally interesting. The present study proved that the cultivar is not a discriminating factor in determining the chemical and biological properties of BS and BW.

Efficacy of Two Moroccan Cistus Species Extracts against Acne Vulgaris: Phytochemical Profile, Antioxidant, Anti-Inflammatory and Antimicrobial Activities

BACKGROUND

The genus Cistus L. (Cistaceae) includes several medicinal plants growing wild in the Moroccan area. Acne vulgaris (AV) is a chronic skin disorder treated with topical and systemic therapies that often lead to several side effects in addition to the development of antimicrobial resistance. Our study aimed to investigate the bioactivity of extracts of two Moroccan Cistus species, Cistus laurifolius L. and Cistus salviifolius L., in view of their use as potential coadjuvants in the treatment of mild acne vulgaris.

METHODS

Targeted phytochemical profiles obtained by HPLC-DAD and HPLC-ESI/MS analyses and biological activities ascertained by several antioxidants in vitro chemical and cell-based assays of the leaf extracts. Moreover, antimicrobial activity against Gram-positive and Gram-negative bacteria, and Candida albicans was evaluated.

RESULTS

Analyses revealed the presence of several polyphenols in the studied extracts, mainly flavonoids and tannins. Cistus laurifolius L. and Cistus salviifolius L. possessed good biological properties and all extracts showed antibacterial activity, particularly against Staphylococcus aureus, S. epidermidis, and Propionibacterium acnes, identified as the main acne-causing bacteria.

CONCLUSION

The results suggest that examined extracts are promising agents worthy of further studies to develop coadjuvants/natural remedies for mild acne treatment.

Mechanical bacterial lysate enhances antimicrobial barrier mechanisms in human airway epithelial cells

Polyvalent mechanical bacterial lysate is effective in the prevention of respiratory tract infections, although its mechanism of action is not entirely elucidated. Because epithelial cells constitute the frontline defense against infections, we investigated the molecular mechanisms of innate response exerted by bronchial epithelial cells in the presence of polyvalent mechanical bacterial lysate. By using primary human bronchial epithelial cells, we observed that polyvalent mechanical bacterial lysate was able to increase the expression of cellular adhesion molecules such as ICAM-1 and E-cadherin, as well as the expression of amphiregulin, a growth factor able to support human bronchial epithelial cell proliferation. Remarkably, polyvalent mechanical bacterial lysate promoted in human bronchial epithelial cells the de novo expression of human β-defensin-2, a major antimicrobial peptide, conferring them a direct antimicrobial activity. Moreover, polyvalent mechanical bacterial lysate-stimulated human bronchial epithelial cells provided signals for increased IL-22 production by innate lymphoid cells via IL-23, which could further contribute to the release of antimicrobial peptides by epithelial cells. In agreement with these in vitro data, the concentration of both IL-23 and antimicrobial peptides (human β-defensin-2 and LL-37) increased in the saliva of healthy volunteers after sublingual administration of polyvalent mechanical bacterial lysate. Altogether, these results indicate that polyvalent mechanical bacterial lysate administration might support mucosal barrier integrity and promote mechanisms of antimicrobial activity in airway epithelial cells.

The In Vitro Potential of 1-(1H-indol-3-yl) Derivatives against Candida spp. and Aspergillus niger as Tyrosinase Inhibitors

Given the increased antimicrobial resistance, global effort is currently focused on the identification of novel compounds, both of natural and chemical origin. The present study reports on the antifungal potential of 1-(1H-indol-3-yl) derivatives, previously known as tyrosinase inhibitors. The effect of seven compounds (indicated as 3a-g) was determined against Candida albicans ATCC 10531, three clinical isolates of Candida albicans, two clinical isolates of Candida glabrata, two clinical isolates of Candida parapsilosis and Aspergillus niger ATCC 16404. The effect of these derivatives on tyrosinase enzymatic activity was also evaluated. Results showed a fungicidal activity of compounds 3b, 3c and 3e against all tested strains at concentrations ranging between 0.250 and 1 mg/mL. Furthermore, the association between 3c and fluconazole and between 3b and caspofungin showed a trend of indifference tending toward synergism. Compound 3c was also able to inhibit microbial tyrosinase up to ~28% at the concentration of 0.250 mg/mL. These data could help provide novel therapeutics for topical use to treat fungal infections and increase the potential effectiveness of the association between novel compounds and commercial antifungals in order to combat drug resistance.

The Digestibility of Hibiscus sabdariffa L. Polyphenols Using an In Vitro Human Digestion Model and Evaluation of Their Antimicrobial Activity

Hibiscus sabdariffa L. (H.s.) is a polyphenolic-rich plant commonly consumed either as a beverage or spice. The aim of the present study was to evaluate the in vitro digestibility of H.s. polyphenols using an in vitro model of digestion which simulates the human stomach and small intestine. The bioaccessible polyphenols released in the digested samples were analyzed by liquid chromatography coupled to photodiode array and mass spectrometry detection. H.s. anthocyanins (cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside) content drastically dropped during the digestion process from 2.91 ± 0.03 µg g⁻¹ and 8.53 ± 0.08 µg g⁻¹ (w/w) CG (Cyanidin-glucoside) in the raw extract, respectively, to 0.12 ± 0.01 µg g⁻¹ 0.12 ± 0.01 µg g⁻¹ (w/w) CG at the end of duodenal digestion. Total polyphenols also have shown a decrease from 1192.65 ± 30.37 µg g⁻¹ (w/w) in the raw extract to 282.24 ± 7.21 µg g⁻¹ (w/w) by the end of gastric digestion, in contrast to their increase by the end of duodenal digestion 372.91 ± 3.97 µg g⁻¹ (w/w). On the other hand, the decrease in certain compounds (e.g., caffeoylquinicandcoumaroylquinic acids) was observed during gastric digestion resulting in an increase of quinic acid in the duodenal aliquots, thus suggesting that this compound was derived from the degradation of the more complex hydroxycinnamic acids. H.s. extract also exhibited a bacteriostatic effect against Staphylococcus aureus ATCC 6538 (MIC of 2.5 mg mL⁻¹) and a bactericidal effect against a food isolate of Listeria monocytogenes (MBC of 2.5 mg mL⁻¹). The undigested polyphenols of H.s. in the upper gastrointestinal tract enters the colon, where they are metabolized by the gut microbiota. The present study results showed that resistance of H.s. polyphenols during gastrointestinal digestion might affect their uptake, resulting in a decrease in their digestibility.

A thermoresponsive gel photoreleasing nitric oxide for potential ocular applications

We report herein the design, preparation, characterization and biological evaluation of a thermoresponsive gel based on binary mixtures of Pluronic® co-polymers F127 and P123, the latter being covalently functionalized with a nitric oxide (NO) photodonor (NOPD). The weight ratio between the two polymeric components is optimized in order to observe gelation of their saline water solution in the range of 32-35 °C, in order to exploit the therapeutic properties of NO for potential ocular applications. Rheological measurements were performed to evaluate the gelation temperature and, hence, to select a co-polymer mixture specifically appropriate for the reference application. Integration of the NOPD into the polymeric scaffold does not affect its rheological and spectroscopic properties, making it a good absorber of visible light both in solution and in the gel phase. Irradiation of the saline solution of the polymeric components with visible light triggers NO release, which occurs with an efficiency of more than one order of magnitude faster than that observed for the isolated NOPD. The polymeric system fully preserves such photobehavior after gelation as demonstrated by the effective NO photorelease from the gel matrix and its diffusion in the supernatant upon illumination. The gel is well-tolerated in both dark and light conditions by corneal cells, while being able to induce growth inhibition towards Staphylococcus aureus under visible light irradiation and has high moduli which can contribute to an adequate retention time within the eyes.

Evaluation of antimicrobial activity of the hydrolate of Coridothymus capitatus (L.) Reichenb. fil. (Lamiaceae) alone and in combination with antimicrobial agents

Background

Hydrolates, complex mixtures containing traces of essential oils (EOs), are inexpensive, easy to make and less toxic than their corresponding EOs. The antibacterial and antifungal activity of the hydrolate of Coridothymus capitatus (L.) Reichenb. fil. (Lamiaceae) alone and in combination with antimicrobial drugs, such as tetracycline and itraconazole, were evaluated.

Methods

The chemical composition was analysed by gas-chromatography-mass spectrometry (GC-MS). Standard methods were performed to evaluate the susceptibility of some Gram-positive and Gram-negative bacteria, and Candida spp. to the hydrolate, in comparison with its EO. The hydrolate mechanism of action was assayed by propidium iodide and MitoTracker staining. Checkerboard tests were carried out for combinations studies.

Results

GC-MS identified 0.14% (v/v) of total EO content into hydrolate and carvacrol as a dominant component. The hydrolate showed a good antimicrobial activity against bacteria and yeasts. It exhibited a synergistic effect with itraconazole against Candida krusei, and an additive effect with tetracycline against methicillin-resistant Staphylococcus aureus strains. Hydrolate changed the membranes permeability of bacteria and yeasts and altered mitochondrial function of yeasts.

Conclusions

Our study extends the knowledge by exploiting non-conventional antimicrobial agents to fight the emergence of antibiotic resistance.

The Antimicrobial and Antiviral Activity of Polyphenols from Almond (Prunus dulcis L.) Skin

Due to their antimicrobial and antiviral activity potential in vitro, polyphenols are gaining a lot of attention from the pharmaceutical and healthcare industries. A novel antiviral and antimicrobial approach could be based on the use of polyphenols obtained from natural sources. Here, we tested the antibacterial and antiviral effect of a mix of polyphenols present in natural almond skin (NS MIX). The antimicrobial potential was evaluated against the standard American Type Culture Collection (ATCC) and clinical strains of Staphylococcus aureus, including methicillin-resistant (MRSA) strains, by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Herpes simplex virus type I was used for the antiviral assessment of NS MIX by plaque assay. Furthermore, we evaluated the expression of viral cascade antigens. NS MIX exhibited antimicrobial (MIC values of 0.31–1.25 mg/ml) and antiviral activity (decrease in the viral titer ** p < 0.01, and viral DNA accumulation * p < 0.05) against Staphylococcus aureus and HSV-1, respectively. Amongst the isolated compounds, the aglycones epicatechin and catechin showed the greatest activity against S. aureus ATCC 6538P (MIC values of 0.078–0.15 and 0.15 mg/ml, respectively), but were not active against all the other strains. These results could be used to develop novel products for topical use.

Feijoa Fruit Peel: Micro-morphological Features, Evaluation of Phytochemical Profile, and Biological Properties of Its Essential Oil

Acca sellowiana (O. Berg) Burret (Feijoa) is an evergreen shrub, belonging to the Mirtaceae family. The aim of this study was to investigate the micromorphological features of the feijoa fruit peel and to evaluate the phytochemical profile, as well as the antioxidant, cytoprotective, and antimicrobial properties of its essential oil (EO), by several in vitro cell-free and cell-based assays. The micromorphological analysis showed several schizogenic secretory cavities, immediately below the epidermal layer. Forty compounds were identified and quantified by GC-FID and GC-MS analyses. Sesquiterpenes were the most abundant ones (76.89%), followed by monoterpene hydrocarbons (3.26%), and oxygenated monoterpenes (0.34%). The main compounds were γ-Selinene (17.39%), α-Cariophyllene (16.74%), β-Cariophyllene (10.37%), and Germacene D (5.32%). The EO showed a strong and dose-dependent antioxidant, and free-radical scavenging activity. Furthermore, it showed cytoprotective activity on the lymphocytes, that have been pre-treated with 100 μM tert-butyl-hydroperoxide (t-BOOH), as well as a decrease in intracellular reactive oxygen species (ROS), induced by t-BOOH on erythrocytes. A preliminary antimicrobial screening against GRAM+ and GRAM− bacteria, as well as on fungi highlighted that EO showed the best activity against S. aureus and C. albicans (MIC 2.7 mg/mL). In light of these results, feijoa fruit EO could find various applications, especially in the food, nutraceutical, and pharmaceutical fields.

Contact Lenses Delivering Nitric Oxide under Daylight for Reduction of Bacterial Contamination

Ocular infection due to microbial contamination is one of the main risks associated with the wearing of contact lens, which demands novel straightforward strategies to find reliable solutions. This contribution reports the preparation, characterization and biological evaluation of soft contact lenses (CL) releasing nitric oxide (NO), as an unconventional antibacterial agent, under daylight exposure. A tailored NO photodonor (NOPD) was embedded into commercial CL leading to doped CL with an excellent optical transparency (transmittance = 100%) at λ ≥ 450 nm. The NOPD results homogeneously distributed in the CL matrix where it fully preserves the photobehavior exhibited in solution. In particular, NO release from the CL and its diffusion in the supernatant physiological solution is observed upon visible light illumination. The presence of a blue fluorescent reporting functionality into the molecular skeleton of the NOPD, which activates concomitantly to the NO photorelease, allows the easy monitoring of the NO delivery in real-time and confirms that the doped CL work under daylight exposure. The NO photoreleasing CL are well-tolerated in both dark and light conditions by corneal cells while being able to induce good growth inhibition of Staphylococcus aureus under visible light irradiation. These results may pave the way to further engineering of the CL with NOPD as innovative ocular devices activatable by sunlight.

Marine Bacterial Exopolymers-Mediated Green Synthesis of Noble Metal Nanoparticles with Antimicrobial Properties

A straightforward and green method for the synthesis of gold, silver, and silver chloride nanoparticles (Au NPs and Ag/AgCl NPs) was developed using three different microbial exopolymers (EP) as reducing and stabilizing agents. The exopolysaccharides EPS B3-15 and EPS T14 and the poly-γ-glutamic acid γ-PGA-APA were produced by thermophilic bacteria isolated from shallow hydrothermal vents off the Eolian Islands (Italy) in the Mediterranean Sea. The production of metal NPs was monitored by UV-Vis measurements by the typical plasmon resonance absorption peak and their antimicrobial activity towards Gram-positive and Gram- negative bacteria (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa), as well as fungi (Candida albicans) was investigated. The biological evaluation showed no activity for EP-Au NPs, except against E. coli, whereas EP-Ag NPs exhibited a broad-spectrum of activity. The chemical composition, morphology, and size of EP-Ag NPs were investigated by UV-Vis, zeta potential (ζ), dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The best antimicrobial results were obtained for EPS B3-15-Ag NPs and EPS T14-Ag NPs (Minimum Inhibitory Concentration, MIC: 9.37-45 µg/mL; Minimum Bactericidal Concentration/Minimum Fungicidal Concentration, MBC/MFC: 11.25-75 µg/mL).

Efficacy of carvacrol against resistant rapidly growing mycobacteria in the planktonic and biofilm growth mode

Rapidly growing mycobacteria (RGM) are environmental bacteria found worldwide with a propensity to produce skin and soft-tissue infections. Among them, the most clinically relevant species is Mycobacterium abscessus. Multiple resistance to antibiotics and the ability to form biofilm contributes considerably to the treatment failure. The search of novel anti-mycobacterial agents for the control of biofilm growth mode is crucial. The aim of the present study was to evaluate the activity of carvacrol (CAR) against planktonic and biofilm cells of resistant RGM strains. The susceptibility of RGM strains (n = 11) to antibiotics and CAR was assessed by MIC/MBC evaluation. The CAR activity was estimated by also vapour contact assay. The effect on biofilm formation and preformed biofilm was measured by evaluation of bacterial growth, biofilm biomass and biofilm metabolic activity. MIC values were equal to 64 μg/mL for most of RGM isolates (32–512 μg/mL), MBCs were 2–4 times higher than MICs, and MICs of vapours were lower (16 μg/mL for most RGM isolates) than MICs in liquid phase. Regarding the biofilm, CAR at concentrations of 1/2 × MIC and 1/4 × MIC showed a strong inhibition of biofilm formation (61–77%) and at concentration above the MIC (2–8 × MIC) produced significant inhibition of 4- and 8-day preformed biofilms. In conclusion, CAR could have a potential use, also in vapour phase, for the control of RGM.

Polyphenolic profile, antibacterial activity and brine shrimp toxicity of leaf extracts from six Tunisian spontaneous species

The aim of this study was to investigate the polyphenolic profile and biological properties of leaves acetonic extracts from six Tunisian spontaneous plants of Marrubium vulgare L., Rhus tripartita (Ucria) D.C., Hernaria fontanesii J. Gay subsp. fontanesii, Ziziphus lotus L., Plantago ovata Forsk., Thymelaea hirsuta (L.) Endl. Bioassay-guided and HPLC-PDA-ESI-MS procedures demonstrated that R. tripartita contained the highest amount of phenolic compounds (1475.1 µg/g), followed by Z. lotus (1087.8 µg/g) and P. ovata (1027.6 µg/g). Interestingly, in R. tripartita myricetin-3-O-galactoside turned out to be the most abundant one. The plant extracts showed antimicrobial efficacy against Listeria monocytogenes, Staphylococcus aureus and S. epidermidis including methicillin resistant strains; no activity was detected against Gram-negative bacteria. R. tripartita revealed the best MIC and MBC values and caused significant decrease of S. aureus biofilm. Both R. tripartita and Z. lotus did not display any toxicity against Artemia salina Leach (LC₅₀ > 1000 μg/mL).

Study of the Lipid Profile of ATCC and Clinical Strains of Staphylococcus aureus in Relation to Their Antibiotic Resistance

A number of reports have indicated a relationship between bacterial resistance to antibiotics and their lipid composition. In the present study, we characterized the lipid profiles of American Type Culture Collection (ATCC) and clinical strains of Staphylococcus aureus and its correlation with antibiotic resistance and hydrophobicity. The following strains were used: S. aureus ATCC 6538P, S. aureus ATCC 43300 (MRSA), seven clinical strains from the pharynges, two strains from duodenal ulcers, four strains from hip prostheses, and one strain from the conjunctiva. Lipid-related differentiation was observed across the S. aureus strains: the higher abundance of anteiso-pentadecanoic acid (anteiso-C_15:0) and anteiso-heptadecanoic acid (anteiso-C_17:0), followed by iso-pentadecanoic acid (iso-C_15:0), suggested that these were common lipids. Iso-tridecanoic acid (iso-C_13:0) and anteiso-tridecanoic acid (anteiso-C_13:0), iso-hexadecanoic acid (iso-C_16:0) and anteiso-hexadecanoic acid (anteiso-C_16:0), and all forms of octadecanoic acid (C_18:0) were usually detected in low abundance. Strains isolated from pharynges showed the highest ratio of branched/straight chains. A distinction in two clusters based on the amount and type of bacterial lipids identified was obtained, which correlated to the antibiotic resistance, the strains origin, and the cell-surface hydrophobicity. We report a potential correlation between the lipid profile of S. aureus strains, site of infection, antibiotic resistance, and cell-surface hydrophobicity. These results, which still need further insights, could be a first step to identifying antibiotic resistance in response to environmental adaptation.

Visible light-activatable multicargo microemulsions with bimodal photobactericidal action and dual colour fluorescence

A microemulsion co-solubilizing a photosensitizer and a NO photodonor in the oily phase can be excited with visible light stimuli resulting in the photogeneration of cytotoxic ¹O₂ and NO together with red and green fluorescence emission.

Antimicrobial Activity of Selected Polyphenols and Capsaicinoids Identified in Pepper (Capsicum annuum L.) and Their Possible Mode of Interaction

Antimicrobial activity of pepper polyphenols and capsaicinoids (Coumarin, caffeic acid, narangin, kaempferol, rutin, quercetin, capsaicin, and dihydrocapsaicin) against 13 pathogen bacteria and three beneficial strains was studied using the disk diffusion and microdilution methods. In general, phenolic compounds had the most important activity with the highest inhibition zones obtained with caffeic acid (3.5-20.5 mm), quercetin (4.75-3.5 mm), and kaempferol (7-14 mm). In the determination of the minimal inhibitory concentrations, the effects of both quercetin and kaempferol were more important than caffeic acid. The clinical strains Staphylococcus aureus (319, 14, 8, 32, and 550) were more sensitive to quercetin (0.00195-0.0078 mg L^-1) whereas kaempferol was more active against the strains S. aureus (ATCC 6538, 26), S. typhimurium ATCC 13311, and Pseudomonas aeruginosa ATCC 27853 (0.0156-0.125 mg L^-1). The interaction between these three polyphenols was studied against S. aureus ATCC 6538 and P. aeruginosa ATCC 27853. Different modes of interaction were observed (synergism, additive, and indifferent), but no antagonism was obtained. The best combination was quercetin and caffeic acid for S. aureus with fractional inhibitory concentration index (FICI) of 0.37, and kaempferol with quercetin for P. aeruginosa (FICI = 0.31).

Effects of adaptation to carvacrol on Staphylococcus aureus in the planktonic and biofilm phases

The effect of exposure to sub-minimum inhibitory concentrations of carvacrol, for either 3-10 days, on direct (carvacrol) or cross-protection (cinnamaldehyde, eugenol, antibiotics) and the influence on planktonic and biofilm growth of four Staphylococcus aureus strains were reported. The sequential exposure to carvacrol resulted in a direct protection that was more evident in two of the four strains after 10 days. No significant cross-protection against cinnamaldehyde, eugenol and antibiotics was detected. An adaptive response was associated with a prolonged lag phase, a lower yield of bacteria, a colony phenotype likely to be associated to small colony variants and an increase in biofilm production. Generally, the biofilm of the adapted strains was less susceptible to subMICs of carvacrol compared to the biofilms of non-adapted strains. In contrast, it was demonstrated that in the case of mature biofilms the susceptibility was similar. The exposure of S. aureus to carvacrol at concentrations above the MIC resulted in a very low mutation frequency.

3,4-DHPEA-EA from Olea Europaea L. is effective against standard and clinical isolates of Staphylococcus sp

Background

The aim of the present work was to evaluate the antibacterial effect of 3,4-DHPEA-EA (methyl-4-(2-(3,4-dihydroxyphenethoxy)-2-oxoethyl)-3-formyl-2-methyl-3,4-dihydro-2H-pyran-5-carboxylate), a derivate of oleuropein, against a range of Gram-positive bacteria, including ATCC strains, food and clinical isolates.

Methods

The minimum inhibitory concentrations (MICs) of 3,4-DHPEA-EA were determined by the broth microdilution method and the Bioscreen C.

Results

3,4-DHPEA-EA was effective against ATCC and clinical isolates of Staphylococcus aureus (MIC values between 125 and 250 μg/ml) and ATCC and clinical isolates of Staphylococcus epidermidis (MIC values between 7.81 and 62.5 μg/ml). No significant differences were observed between the two solvents (methanol and DMSO) used to dissolve 3,4-DHPEA-EA.

Conclusions

The results obtained could be used to develop novel therapies for the treatment of skin infections. Further studies need to be performed to elucidate the formation of 3,4-DHPEA-EA by acid hydrolysis of oleuropein in the human stomach.

Staphylococcal biofilm formation as affected by type acidulant

Staphylococcal growth and biofilm formation in culture medium where pH was lowered with weak organic (acetic and lactic) or strong inorganic (hydrochloric) acids were studied. The effects were evaluated by biomass measurements, cell-surface hydrophobicity, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). The results demonstrated that the inhibition was related to type of acidulant and pH value. At pH 5.0, the antibacterial effect was more pronounced in the presence of acetic acid (58-60% growth reduction) compared with that in the presence of lactic (7-16% growth reduction) and hydrochloric acids (23-24% reduction). The biofilm biomass of Staphylococcus aureus and Staphylococcus epidermidis was reduced by 92, 85, 63, and 93, 87, 81% after exposition to acetic, lactic, and hydrochloric acids, respectively. Increasing the pH from 5.0 to 6.0 resulted in a noticeable reduction in the effectiveness of acids. A minor cells hydrophobic character was also documented. The SEM and CLSM revealed a poorly structured and thinner biofilm compared with the dense and multilayered control. Acidic environment could have important implications for food-processing system to prevent bacterial colonization and control biofilm formation. The findings of this study lead to consider the rational use of the type of acid to achieve acidic environments.

Norfloxacin and ursolic acid: in vitro association and postantibiotic effect against Staphylococcus aureus

AIMS

We investigated the effectiveness in vitro of the association between norfloxacin (NOR) and ursolic acid (UA) against Staphylococcus aureus.

METHODS AND RESULTS

The minimal inhibitory concentrations (MICs), the minimal bactericidal concentrations, the bacterial killing and the postantibiotic effect (PAE) of NOR and UA were determined both singly and in combination. A synergistic interaction was observed against Staph. aureus ATCC 29213: the mean PAEs were 3 h for NOR, -1.2 h for UA (1 × MIC) and 2.0 h for UA (2 × MIC). Synergism was observed with longer PAEs and postantibiotic sub-MIC effects after NOR/UA exposure. UA was also active against clinical isolates and methicillin-resistant Staph. aureus.

CONCLUSIONS

The application of antimicrobial combinations may address the rising resistance to established classes of both systemic and topical agents.

SIGNIFICANCE AND IMPACT OF THE STUDY

In vitro interactions between NOR and UA may contribute to the development of novel topical agents for the treatment of skin infections as well as for topical formulations.

In vitro protective effects of two extracts from bergamot peels on human endothelial cells exposed to tumor necrosis factor-alpha (TNF-alpha)

Bergamot ( Citrus bergamia Risso) is a less commercialized Citrus fruit, mainly used for its essential oil extracted from the peel. Bergamot peel (BP) represents about 60% of the processed fruits and is regarded as primary waste. However, it contains good amounts of useful compounds, such as pectins and flavonoids. Many of the bioactivities of Citrus flavonoids appear to impact vascular endothelial cells. Herein, we report the protective effect of two flavonoid-rich extracts from BP (endowed with radical-scavenging properties and lacking genotoxic activity) against alterations in cell modifications induced by the pleiotropic inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) on human umbilical vein endothelial cells (HUVECs), as demonstrated by monitoring intracellular levels of malondialdehyde/4-hydroxynonenal, reduced and oxidized glutathione and superoxide dismutase activity, and the activation status of nuclear factor-kappaB (NF-kappaB). Thus, BP appears to be a potential source of natural antioxidant/anti-inflammatory phytocomplexes to be employed as ingredients of nutraceutical products or functional foods.

Antimicrobial potential of polyphenols extracted from almond skins

AIMS

To evaluate the antimicrobial properties of flavonoid-rich fractions derived from natural and blanched almond skins, the latter being a by-product from the almond processing industry.

METHODS AND RESULTS

Almond skin extracts were tested against Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Serratia marcescens), Gram-positive bacteria (Listeria monocytogenes, Enterococcus hirae, Staphylococcus aureus, Enterococcus durans) and the yeast Candida albicans. Almond skin fractions were found to have antimicrobial activity against L. monocytogenes and Staph. aureus in the range 250-500 microg ml(-1), natural skins showing antimicrobial potential against the Gram-negative Salm. enterica. The interactions between three almond skin flavonoids were also evaluated with isobolograms.

CONCLUSIONS

Pairwise combinations of protocatechuic acid, naringenin and epicatechin showed both synergistic and indifferent interactions against Salm. enterica and Staph. aureus. Antagonism was observed against L. monocytogenes with all combinations tested. Further studies need to be performed to understand the mechanisms responsible for these interactions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Almond skins are a potential source of natural antimicrobials.

Control of biofilm formation by poly-ethylene-co-vinyl acetate films incorporating nisin

The aim of this study was to evaluate the effect of poly-ethylene-co-vinyl acetate (EVA) films incorporating different concentrations (0.1%, 0.5% and 1%) of nisin on the biofilm-forming ability of Listeria monocytogenes ATCC 7644, Staphylococcus aureus 815 and Staphylococcus epidermidis ATCC 35984. Nisin was incorporated into two grades of EVA (EVA14 and EVA28) in the melt during a common film-blowing operation. The efficacy of EVA/nisin films was evaluated by biofilm biomass measurements and Live/Dead staining in combination with fluorescence microscopy. In order to evaluate whether the nisin incorporation could modify the film surface properties, contact angle measurements and scanning electron microscopy were performed. The results revealed the efficacy of EVA14/nisin films in reducing biofilm formation on their surfaces with more evident effect for S. epidermidis than L. monocytogenes and S. aureus strains. In contrast, EVA28/nisin films showed unsatisfactory activity. Fluorescence microscopy confirmed poor biofilm formation on EVA14/nisin films, also characterised by the presence of dead cells. The data presented in this study offer new potential applications for developing strategies aimed to improve the effect of antimicrobial agents.

Synergism and postantibiotic effect of tobramycin and Melaleuca alternifolia (tea tree) oil against Staphylococcus aureus and Escherichia coli

The application of antimicrobial combinations may address the rising resistance to established classes of both systemic and topical agents and their clinical relevance is related to the presence of a significant postantibiotic effect (PAE). We investigated the effectiveness in vitro of the association between tobramycin and tea tree oil (TTO) against Gram-positive and Gram-negative bacteria. The minimal inhibitory concentrations, the bacterial killing and the PAE of tobramycin and TTO were determined both singly and in combination against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213. A synergistic interaction was observed against both strains tested: the mean PAEs were 1.3 and 1.7h for tobramycin against E. coli and S. aureus respectively, 10.8h for tobramycin and TTO (0.05%) against E. coli, 10.4h and 17.4h against S. aureus for tobramycin and TTO (0.25 and 0.50%, respectively). Longer PASMEs were observed with S. aureus after TTO/tobramycin exposure. In vitro interactions can improve the antimicrobial effectiveness of the antibiotic and may contribute for the development of novel topical agents for the treatment of skin lesions including conjunctiva and respiratory infections by inhalation.

Anatomical, chemical, and biochemical characterization of cladodes from prickly pear [Opuntia ficus-indica (L.) Mill.]

Opuntia ficus-indica cladodes represent the green stem of the plant and are generally used as animal feed or disposed of in landfills. The present work investigated the anatomical and chemical composition of Opuntia cladodes, which form the basis of their pharmacological effects. Glucose and galacturonic acid were the main sugars of Opuntia cladodes, whereas high-performance liquid chromatography (HPLC) analysis showed the presence of mainly kaempherol and isorhamnetin glycosides (glucoside and rhamnoside). The presence of high amounts of calcium oxalate crystals was demonstrated by light microscopy on fresh and lyophilized cladodes. No antimicrobial activity was observed even after enzymatic treatment. O. ficus-indica cladodes may retain material tightly associated with cell-wall components, and this property will have the potential to greatly reduce the bioavailability of bioactive compounds.